Does the zodiac really have anything to do with who your friends are? To tackle this question once and for all, Slate Labshas built an application that tallies up the signs for all of your friends who list their birthday and calculates the percentage of them who have signs that the zodiac says are compatible with yours. Every sign is compatible with five others and semi-compatible with another two, meaning that if your friends' birthdays were randomly distributed, you would expect 58 percent of your friends to be compatible with you.  If astrology is "true" for your friends, you should see a score much higher than 58 percent. Of course, most of us aren't actually friends with all of our Facebook comrades, so if you want the most accurate score then you can tell the app who to tally and who to leave out. Just uncheck people who you don't know or dislike in the right-hand box and click "recalculate." Leave at least 10 friends checked to see results.

Privacy note: This app will never post to your wall or bug your friends. We'll keep track of aggregate scores for the sake of curiosity, but we will not record your Facebook ID or any other identifying information.